Multiple transformer arrangement



Dec. 8, 1931. A. o. AUSTIN 1,335,201

MULTIPLE TRANSFORMER ARRANGEMENT Filed March 16, 1927 1 N V EN TOR.

BY Mam i/w ATTORNEYS ARTHUR O. AUSTIN, OE BA RBERTON, OHIO, ASSIGNOR TOTHE OHIO BRASS COMPANY,

Patented Dec. 8, I931 UNITED STATES PATENT OFFICE OF MANSFIELD, OHIO, ACORPORATION OF NEW JERSEY MULTIPLE TRANSFORMER ARRANGEMENT Applicationfiled March 16, 1927. Serial No. 175,655.

This invention relates to arrangement of high potention transformersdeveloping volttransformers. Other objects and advantages will appearfrom the following description andclaims. Theinvention is exemplified inthe combination and arrangement of parts shown in the accompanyingdrawings and described in thefollowing specification, and

it is more particularly appended claims.

In the drawings-- I Fig. 1 is a diagrammatic view illustrating oneembodiment of the present invention.

Fig 2 is a view similar to Fig. 1 showing a sli htly differentarrangement.

pointed out in the that is ratio of voltage at full load to that at noload. Astill further consideration is the power or k. -v. a. output ofthe transformer or combination of transformers. A

still further consideration is the provision of a: suitable arrangementof transformers and apparatus, sothat the required high voltage damageto'thetransformer. p One of the most effective'ways 1n protecting atransformer, particularly one used unig. 3' is a diagrammatic viewshowing the der the severe conditions of high voltage testing, is toinsert a resistance in, series with the high voltage winding. Thisresistance must be ofafairly high value, as a comparatively smallcurrent in the high voltage winding may set up very severe conditionswithin the transformer winding. It is therefore necessary that acomparatively high resistance be used so that it will tend to absorb anydisturbance tending to damage the transformer.

With the ordinary concatenated or chain connection, where a few endturns of one transformer are used to excite the next transformer in thechain or series, it is exceedingly dlflicult or practically impossibleto provide resistance protection. This is due to the fact that the fewturns must carry a large current as compared to that produced by theload in the high tension winding. If a resistancewere inserted in theseleads which have to carry the heavy exciting current, much energy wouldbe absorbed and the re ulation of the transformer chain would Ea verypoor.

In order to improve the regulation and power or k. v. a. output and atthe same time provide suitable protection to the transformers, I havedevised anew scheme or arrangement for a combination of transformers.One such arrangementis shown in Fig. 1. Suitable transformers, A, B andC are provided dent, however, that any other point might be groundedorthe end of the winding grounded on the case. When one end of the highvoltage winding is grounded onthe case, gend power outputmay b v bt i dith t gerator 16 may be mounted at any convenient point and need notbeinsulated from ground. Where, the center point of the transformer isgrounded, itis usually advisable to mountthe with high tension windings10, 11 and 12, and primary or low tension windings 13, 14 and lit)generator on the transformer tank or on a suitable insulated base.

vVhere the generators are insulated, it is necessary to drive thegenerators by a suitably insulated shaft 38 or belt 87. Where the highvoltage windings are arranged in chain connection, the severalgenerators may be driven by belts or by induction motors, the slip inthe belt or induction motor providing the necessary distribution of theload among the several generators, as the chain connection will tend tomaintain the proper phase relation.

In the ordinary chain or concatenated connection, the amount of power ork. v. a. output is limited to that of the smallest or most highly workedtransformer in the chain. If, therefore, three transformers of the samesize were connected in series or in chain forma tion, the total 1;. v.a. output would be that of a single transformer only, whereas with myimproved connection, the k. v. a. output would be the total of all thetransformers, or three times the amount. This in itself is a very greatadvantage, particularly where it is desired to keep down the cost of thetransformers for a given output or where it is desired to obtain a largeoutput, as in the case of power work.

In Fig. 1 the connections between the points 19 and 20, or 21 and 22,will have little or no current except that produced by the load, or thatrequired to keep the several transformers in proper phase relation.Since the amount of current produced by the load at very high voltage isexceedingly small, and the current flowing between the two transformersis very small compared to that in the ordinary chain connection, the endor exciting turns between the points 21 and 19 and 22 and 20, may havemuch smaller current carrying capacity than in the case of the ordinaryconcatenated or chain form. This results in a considerable saving.

Since the current flowing in the conductors between the two transformersis comparatively small, it is possible to insert comparatively highresistances, 31., in all of the leads connecting the transformerstogether, as well as to the load and to ground. The fact that theseresistances may be of appreciable magnitude, makes it possible to absorbthe energy in small currents which might otherwise cause destruction ora breakdown in the insulation of the transformer. This is particularlytrue in testing conditions where the transformer windings are likely tobe impressed with very severe volta es set up by high voltage discharges.

' Once the transformers and generators are in proper phase relation, aslight load on the series will usually tend to maintain proper phaserelation. It is evident that where the load or current flowing throughthe high voltage winding of the transformers will shown in Fig. 2.

maintain them in synchronism, the chain or concatenated connection maybe dispensed with and the transformers operated in a direct series.Where the core and case of one or more of the transformers are insulatedfrom ground and connected to the high tension windings, as in Fig. l,the core and ease form with the ground a condenser which receives itscharging current from the high tension winding, thus placing sufiicientcapacitance load on the transformers to hold the several units in stepafter they have once been synchronized even though there is no otherload on the transformers. The concatenated arrangement can be used tofacilitate starting up, and phasing of the transformers. After this, theexciting connection between the transformers may be dispensed with and adirect connection between the end turns of adjacent transformersestablished as between 19 and 22, and 26. In order to do this, asuitable disconnecting switch, 32 and 33, must be opened and connectionmade at 34.

It is e ident that this arrangement may be established in a variety ofways. By using a suitable reactance 35 in one of the circuits, theconnection 3-l can be established before switch or 38 are opened. Afterswitches 33:. and 33 are opened and closed,the full voltage of eachtransformer is added to the next, which gives a somewhat higher voltagethan where the concatenated or chain arrangement is used. The casing andcore of the various transformers is diagrannnatically represented at 36.g V

\Vhere suitable drives are provided to control the speed of the severalgenerators, either by driving through synchronized motors attached byshafts, or oy manual speed control using various speeds in the drivingmotors, or by automatic speed control so that the various transformersare given the proper phase relation, it is apparent that the ordinarycon.- catenated or exciting winding is unnecessary, even for startingup. This arrangenient is In Fig. 2 the transformers D, E and F areconnected through resistances elO and ti, and to the ground and load byresistances d2 and 43. It is evident that either. the center or one endof the high voltage winding may be grounded on the case, as desired, orto conform with the apparatus which is desired to connect up. It is alsoevident that part of the transformers might be grounded at one end onthe case, and part grounded at the center on the case, withoutmaterially affecting the arrangement. lVhile the resistances may varyconsiderably with the apparatus one quarter of an ohm to an ohm per voltgenerated can be used, without appreciable effect upon the regulation,and this will afford material protection to the transformer againststeep wave fronts or high frequency disturbances in the insulation,

Where the centers of transformers D, E and F are connected to therespective'cases, it is necessary to insulate the transformers andexciting generators in accordance with the voltage to ground. Thearrangement shown in Fig. 2 gives the full accumulated voltage of all ofthe transformers and the full k. v. a output. Where the transformers areof equal size, the k. v. output will be three times that of the chainconnection and the voltage regulation will be as good for the series asfor a single transformer. The improved regulation and power output areof considerable value in determining test results for high voltageresearch work. The multiple excitation with insulated generators is adecided advantage over the chain excitation in that the power out-put ofthe several transformers is accumulated and not limited to the smallertransformer or the very highly loaded one in the chain.

The highest voltage in the transformer winding with respect to ground,may be electrically connected to the case rather than the low side.Where the connection is made up in this way, the large surface of thetransformer case can be utilized to reduce the concentration of stressin the air and further act as a condenser for supplying additionalenergy for high voltage or impact tests. The case and core of thetransformers are represented diagrammatically in each instance at 45.

The method can be used to advantage for raising the voltage andincreasing the power output or for regulating the voltage fortransformer work. With the scheme as outlined, it is, of course,necessary to insulate the generator from ground for the voltagegenerated by the succeeding transformer or transformers. For power work,it is, of course, necessary to provide an insulated coupling of suitablesize for transmitting the power from the prime mover to the generator,but even where the voltage is comparatively high, this need not be aserious factor.

An arrangement suitable for a transmission line is shown in Fig. 3,which illustrates one phase of a polyphase system. In this figure, Grepresents the first transformer in the series and H the boosting orregulating transformer in the series. The high voltage winding 50 of thefirst transformer has one end connecting to ground or to the neutral.The low voltage winding 51 is connected to one phase of the generators.The high voltage winding is provided with suitable end turns 52 whichare connected with suitable end turns 53 of the high voltage winding 54of transformer H, or if desired, the leads from the end turns 52 may beconnected to the low voltage winding 55 of transformer H. this windingbeing arranged in series with the winding 54 providing, of course, thatthe voltages generated are suitthe advantage that special able. Thisarrangement makes it possible to use the old transformers on a systemgreatly increasing the power output and at the same time maintains thegood regulation which would normally be much poorer with the secondtransformer operated'entirely as an auto transformer from the first. Theconnection between the end turns of the transformers G and-H will keepthe two transformers in phase. I

If the insulated generator 5610f transformer H is not driven, it willact as amotor and could be used in this connection at'the receiving endfor either taking off power or the control of voltage. I

The generator connected to transformer H is of course, a single'phasegenerator insulated from the round. The exciter: for this generator is onecessity insulated from ground. Even where "the first transformersenergize a 110 k. v. transmission line, the provision of insulation forthe transformers and the construction ofa suitable insulating couplingfor the generator, even for large amounts of power, is not a seriousproblem.

The reason for this is that the-margin of insulation required at the lowside of the high tension winding, as compared'to the side connected tothe line, need not be very high, as linesurges produced by. lightning,switching or grounds are damped'out-by the high voltage winding,'andwhile these volt ages are very high on the side line, the risein voltageon the low side ofthe windingwill be comparatively slight 'underoperating conditions. A 110 kvtransmission system has approximately65,000 volts to'ground. The surges coming in from the transmissionlinemay be exceedingly high, running 'to'several hundred-thousand volts andin some'cases, probably exceeding a million'voltsilf' the insulatedgenerator were subjectedtothis voltage, the insulated coupling wouldnecessarily have to be exceedingly large to'provide a sufficient factorof safety sothat' 'the arrangement would not be practicable. \Vith thearrangement shown in-Fig. 3 however, the transformer 'H will absorb thevery high voltages so that the generator and insulated coupling willhave to provideonly a reasonable margin of safetyfon-the165,000

volts normally. imposed upon the coupling and generator.

Where it is possible generator 56 and the generatorenergizing thewinding 51 of transformer. G: from the same prime mover, itisunnecessary tOEprovide the auto transformer connection betweentransformer G and transformer "The arrangement being practicallythatsliown in Fig. 2 with the exception th at the resistande 40 would beomitted, vthis arrangement[has I tra n'sf'orme r si are notrequired andold transfo used as part of the chain. 1

" lao In of is evident that synchronizing of the transf rmers, securedbyd iving the en rat rs er the ifile ent primary windings frame commonprime mover 60, in

' anes I win ha e.bettrefiieiencnlower cost and better resale. 1.1. I f

omputation showingtherelative regu- 7 gatingor concatenated or chainarrangement of e a, S o mers as c mp tothe 11' ent in ention, sh a e ofthelatterivhene close regulation is desired for tra 'sswnsor te ti gg enser es fthreeransformers using the ordinary chain co nee nhas anestimated regulation of going from full load leading current to fal loalagging ur T same series oftransformers with the 1mprored multiple exc ti n un e the am load cond tions, h s a e tim or she ge in voltage of1.28 percentronly. The r ed connection has the same regulation of 1.28pernent'for a'series of four f hile the same four transform-- h}; ,rnary chain connection has regulation of 3 pe for the changes load. 7 r i1,- In col bination, plurality of trans-' formers haying theirhigh'potential windings connected in series, means for separately enei gthe low potent al windings of two of said transformers, said excitingmeans being energized from asource other than t e dings ofsaidtransformers to avo d lugh current values said transf mer wmdmgs and aresistance'in se e W hf high P tei tial wi dings o said t n o ofsufiicient vane to he eifective in materially reducinglsurges in saidwindings.

2. In combination, a plurality of transformers having their highpotential windings in' seri es, alternators for energizing thelowpotential winding-s oftWo of said transformers, the alternator forthe transformer V havingthe higher potential position in saidseriesf'heing insulated from the earth and a 'resistanceinterposed inseries withth'e high potential windingsof said transformers.

3.'In combination, a pluralityof transforme' fvs havingthe r h gh pote lWin ings connectedinser es,g n r tors for sep rately energizing the lowpotential windings of. two of said transformers, the generator for thetransformer having the higher potential position in said series beinginsulated from the earth and resistance interposed in ser es w1thsa1dhigh potential windings, the

minimum amount of said resistance being approximately one-quarter, ofone ohm per 'volt generatedby said secondary windings.

, 4:. In combination, aplurality of transformers having end turns of-thehigh potential winding of one connected -in parallelj with endturns ofthe high potential windng of another, to assistin maintaming synchronismbetween said transformers, alternators for separately energizing the lowpotential windings Of SllQl transformers and re sistance interposed inthe connections betweensaid end turns. V p v 5. In combination, aplurality of transformers, an end turn the high potential end of th ehigh potentialwinding of one of said transformers being connected in.parallel with an end turn at thelow potential end of the high potentialwinding. ofanother of said transformers, alternator-s for separatelyenergizing the low potential windings of said transformers and switchesfor changing the connection between said high potential windings toplace all of the turns of said high po-' tential windings in series.

6.In combination, a plurality oftransformers having turns of their highpotential windings connected in parallel to assist in mainta ningsynchronlsm between-sa d trans- V formers, means for separatelyenergizing the low potential windings of said transformers,

resistance interposed in the connections between sald high potent1alwindings and switches for changing the connection between said highpotential windings to place all of the turns thereof in series.

7, In combination, a plurality of transformers having their highpotential windings arranged in series with end turns of adjacenttransformers in said series connected in parallel, means forseparatelyenergizing the low potential 'indings to said transformers andm'ea (s forchanging the connections between the high potentialwindingsof said transformers to place allof the high potential windingsofsaid transformers in series. V

8. Incombination, 'a plurality 10f transformers having-their highpotentialwindin gs arrangedinseriesandIlia 11g endturns of the highpotential windings of Cachacent transformers connected in parallel,resist ances interposed in the connections between saidhigh potentialwindings, means for separa-tely energizing the low potential windings ofsaid transformers, switches for changing the connections between saidhighpotential windings to place all of the turns of said hlgh potentialwind ngs-1n seriesand inductive resistance arrangedinseries with certainof said switches to prevent surges when said switches are operated.

9. In combination, a pair of transformers having their high potentialwindings arranged in series and connected to a transmission line, meansfor separately energizing the low potential windings of saidtransformers, the high potential Winding of the transformer having thehigher potential position in said series, being interposed between theline and said means for energizing the low potential windings of saidtransformers to protect said energizing means from. surges in thetransmission line.

10. In combination, a pair of transformers having their high potentialwindings connected in series and connected to a transmission line, thetransformer next adjacent said transmission line being provided with ahigher degree of insulation than the other of said transformers towithstand the effect of surges in said transmission line, and means forseparately energizing the low potential windings of said transformers,said energizing means for the transformer having the higher potentialposition in said series being insulated from the earth and protectedfrom surges in said line by the high potential windings connected withsaid line.

11. In combination aplurality of transformers having their high tensionwindings connected in series, one end of the series of high tensionwindings being grounded, each transformer having its high tensionwinding connected to the core and case of the transformer, a separatealternator electrically connected with the low tension winding of eachof said transformers and resistance in series with said high tensionwindings, the alternators for the transformers having higher potentialpositions in said series having their frames insulated from ground.

12. In combination a plurality of transformers having their high tensionwindings connected in series, independently driven means for excitingthe low tension windings of said transformers, and means connected withsaid high tension windings for subjecting said windings to a capacitanceload for maintaining said transformers and their driving means in step.

13. In combination a plurality of transformers having their high tensionwindings connected in series one point in the high tension circuit thusformed being grounded, independently driven exciters for exciting thelow tension windings of said transformers, and means connected with saidhigh tension circuit at a point removed from the grounded point thereoffor subjecting said high tension circuit to a capacitance load.

14. In combination a plurality of trans formers having their hightension windings connected in series, one end of the series circuit thusformed being grounded, independay

